A Smoky Mountains 101 guide to make the most of your visit. Great Smoky Mountains National Park, spanning the North Carolina–Tennessee border, is the most visited national park in the United States, drawing more than 12 million people each year (Grand Canyon ranks second with about 5 million). Step beyond the bustle, though, and a different world opens up. US 441 slices straight through the park, funneling commuters and pass-through travelers who never hit a trail. What makes the Smokies truly extraordinary, however, is their astonishing biodiversity, the very quality that earned the park UNESCO World Heritage status in 1983.